How to replace a black background with a transparent from exr image?

as you see in my image i exported my emit layer to exr file

then i reviewed it inside my compositor and i can review it inside blender as you see but the problem is im trying to convert it to transparent image but every time i failed i tried to use this emit layer to be over another pure alpha image but when i export it to png i can’t see the laser only the transparent background i tried to open the exr file on photoshop but still nothing there only black image and another ways and all failed

Shouldn’t need to have it transparent when the image is added on top of another image. Black is 0 so it won’t affect the image.

But yea, set alpha node can make it transparent.